In some patients, some subchondral voids are formed in the bone structure at joints, which voids may weaken the bone. The voids are typically in the trabecular bone structure. In such cases, for some patients, it may not be necessary to use implants, as the injection of a compound in such voids may suffice in solidifying the bone. It would be desirable to use computer assistance to render subchondral injection minimally invasive and ensure the adequate injection of compound or filler material in bone voids.